swift

9cb9ebda - [Backtracing][Linux] Fix crash handler for musl.

[Backtracing][Linux] Fix crash handler for musl. Musl's `clone()` wrapper returns `EINVAL` if you try to use `CLONE_THREAD`, which seems a bit wrong (certainly it is in this particular application, since we *really* don't care whether the thread is a valid C library thread at this point). Also properly support ELF images that are built with a base address other than zero (this typically isn't an issue for dynamically linked programs, as they will be relocated at runtime anyway, but for statically linked binaries it's very common to set the base address to a non-zero value). rdar://154282813